Gaseous reaction mechanism of C₂F radical with water

Abstract

The kinetic properties of the carbon-fluorine radicals are little understood except those of CFn (n =1-3). In this article, a detailed mechanistic study was reported on the gas-phase reaction between the simplest pi-bonded C2F radical and water as the first attempt to understand the chemical reactivity of the C2F radical. Various reaction channels are considered. The most kinetically competitive channel is the quasi-direct hydrogen-abstraction route forming P5 HCCF + OH. At the CCSD(T)/6-311+G(2d,2p)//B3LYP/6-311G(d,p)+ZPVE, CCSD(T)/6-311+G(3df,2p)//QCISD/6-311G(d,p)+ZPVE and Gaussian-3//B3LYP/6-31G(d) levels, the overall H-abstraction barriers (4.5, 4.7, and 4.2 kcal/mol) for the C2F + H2O reaction are comparable to the corresponding values (5.5, 3.7, and 5.7 kcal/mol) for the analogous C2H + H2O reaction. This suggests that C2F is a reactive radical like the extensively studied C2H, in contrast to the situation of the CF and CF2 radicals that have much lower reactivity than the corresponding hydrocarbon species. Thus, the C2F radical is expected to play an important role in the combustion processes of the carbon-fluorine chemistry. Furthermore, addition of a second H2O can catalyze the reaction with the H-abstraction barrier significantly reduced to a marginally zero value (0.5 kcal/mol). This is also indicative of the potential relevance of the title reactions in the low-temperature atmospheric chemistry.

Theoretical prediction of new dipole-bound singlet states for anions of interstellar interest

“…64 We therefore conclude that no dipolebound singlet excited state of C 3 N − exists. While C 2 F − is linear, the C 2 F neutral radical 86,87 [see Fig. 1(g)] is bent at 154.9 • , yielding an eBE of 3.17 eV at the CCSD(T)/aug-cc-pVTZ level of theory and a relatively small dipole moment of 1.075 D. However, the linear radical (which is not a minimum on the potential surface) has a much larger dipole moment of 2.403 D. This is not enough, however, to stabilize the lowest singlet excited state, as the EOM-CCSD/d-aug-cc-pVDZ adiabatic transition energy is 3.51 eV, well above the required threshold.…”

Infrared spectrum of elusive C2F radical: A matrix-isolation and computational study

“…A few computational attempts to consider C 2 F radical are known whereas practically no experimental data are available [1,2]. The main motivation of the present work is to identify the infrared (IR) absorption spectrum of C 2 F radical using the matrixisolation technique supported by high-level calculations.…”